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Grapes have been intertwined with human history for millennia, providing the basis for wines made by our ancestors thousands of years ago – but that might not have been the case if the dinosaurs hadn’t been wiped off the face of the planet, according to new research.
When an asteroid hit Earth 66 million years ago, it wiped out the massive, rumbling animals and set the stage for other creatures and plants to flourish in its wake.
Now, the discovery of fossilized grape seeds in Colombia, Panama and Peru that range from 19 million to 60 million years old is shedding light on how these humble fruits gained a foothold in Earth’s dense forests and eventually created a global presence. One of the newly discovered seeds is the oldest example of a plant from the grape family found in the Western Hemisphere, according to a study of the specimens published Monday in the journal Nature Plants.
“These are the oldest grapes ever found in this part of the world and are several million years younger than the oldest ever found on the other side of the planet,” said lead study author Fabiany Herrera, an assistant curator of paleobotany at the Field Museum at Chicago’s Negaunee Integrative Research Center, in a statement. “This discovery is important because it shows that after the extinction of the dinosaurs, grapes really began to spread around the world.”
Like soft animal tissues, actual fruits are not well preserved in the fossil record. But the seeds, which are more likely to fossilize, can help scientists understand what plants were present at different stages of Earth’s history as they reconstruct the tree of life and create origin stories.
The oldest grape seed fossils ever found were discovered in India and date back to 66 million years ago, around the time of the dinosaurs’ demise.
“We always think about the animals, the dinosaurs, because they were the biggest things that were affected, but the extinction event also had a big impact on the plants,” Herrera said. “The forest was restored in a way that changed the composition of the plants.”
Herrera’s doctoral advisor, Steven Manchester, who is also a senior author on the new study, published a paper about grape fossils found in India. It inspired Herrera to ask where other grape seed fossils might exist, such as South America, although they had never been found there.
“The grape has an extensive fossil record that starts about 50 million years ago, so I wanted to discover one in South America, but it was like looking for a needle in a haystack,” Herrera said. “I’ve been searching for the oldest grape in the Western Hemisphere since I was a student.”
Herrera and study co-author Mónica Carvalho, assistant curator at the University of Michigan Museum of Paleontology, were doing fieldwork in the Colombian Andes in 2022 when Carvalho spotted a fossil. It turned out to be a 60-million-year-old grape seed fossil trapped in rock, among the oldest in the world and the first to be found in South America.
“She looked at me and said, ‘Fabiany, a grape!’ And then I looked at him, I said, ‘Oh my God.’ It was so exciting,” Herrera said.
Although the fossil was small, its shape, size and other features helped the pair identify it as a grape. And after returning to the laboratory, the researchers performed CT scans to study its internal structure and confirm their findings.
They named the newly discovered species Lithouva susmanii, or “Susman’s stone grape,” in honor of Arthur T. Susman, who has been a supporter of South American paleobotany at the Field Museum.
“This new species is also important because it supports a South American origin of the group in which the common Vitis grape vine evolved,” said study co-author Gregory Stull of the National Museum of Natural History.
The rocks were deposited in lakes, rivers and ancient coastal environments, Herrera said.
“To look for such small seeds, I took apart every available piece of rock in the field,” he said, adding that the difficult search “is the fun part of my job as a paleobotanist.”
Encouraged by their find, the team carried out more fieldwork across South and Central America and found nine new species of fossil grape seeds trapped within sedimentary rocks. And by tracing the ancestry of the ancient seeds to their modern grape counterparts, the team realized that something had enabled the plants to flourish and spread.
When the dinosaurs went extinct, their absence changed the entire structure of the forests, the team hypothesized.
“Large animals, such as dinosaurs, are known to change the ecosystems around them. We think that if there were large dinosaurs roaming the forest, they likely felled trees, effectively keeping the forests more open than they are today,” Carvalho said.
After the dinosaurs disappeared, rainforests grew and layers of trees created an understory and canopy. These dense forests made it difficult for plants to get light and they had to compete with each other for resources. And climbing plants had an advantage and used it to reach the canopy, the researchers said.
“In the fossil record, we start to see more plants using vines to climb trees, like grapes, around this time,” Herrera said.
Meanwhile, as a diverse group of birds and mammals began to populate the Earth after the extinction of the dinosaurs, they likely also helped spread grape seeds.
The study of seeds tells a story of how grapes spread, adapted and disappeared over thousands of years, showing their resilience to survive in other parts of the world despite disappearing from Central and South America over time.
Some fossils are related to modern grapes and others are distant relatives or grapes native to the Western Hemisphere. For example, some of the fossil species can be traced back to grapes found only in Asia and Africa today, but it’s unclear why grapes became extinct in Central and South America, Herrera said.
“The new fossil species tell us a turbulent and complex history,” he said. “We usually think of diverse, modern rainforests as a ‘museum’ model, where all species accumulate over time. However, our study shows that extinction has been a major force in the evolution of tropical forests. Now we need to identify what caused those extinctions over the last 60 million years.”
Herrera wants to look for other examples of fossil plants, such as sunflowers, orchids and pineapples, to see if they existed in ancient rainforests.
Studying the origins and adaptations of plants in the past is helping scientists understand how they might fare during the climate crisis.
“I only hope that most living plant seeds adapt quickly to the current climate crisis. The fossil seed record tells us that plants are resilient, but they can also completely disappear from an entire continent,” Herrera said.